At least 59 people are dead and 527 injured after a 72-minute shooting by a lone-wolf gunman who unleashed thousands of rounds of ammunition onto a Las Vegas music festival from a hotel room 365m away - and more details are still coming out.

Police say 64-year-old Stephen Craig Paddock used automatic weapons to rain down gunfire on a crowd of 22,000 people attending the Route 91 Harvest Festival Sunday night, from his room across the street in the Mandalay Bay hotel.

Police found more than 19 rifles in his hotel room, along with hundreds of rounds of ammunition, a law enforcement official confirmed.

Two guns were mounted on tripods at the windows.

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Headliner Jason Aldean was in the middle of his set when gunfire rang out, the sounds of screams and stampeding humans cutting through the country music on Monday night (NZ time).

It took police an hour and 12 minutes from the first 911 call to find Paddock.

They quickly figured out the shots were coming from the Mandalay Bay, and the smell of gunsmoke from the hundreds of rounds Paddock fired led police to his room.

They used explosives to blow the door off his room, but by then it was too late - Paddock had shot himself dead. It's unclear how long after he first started shooting that he committed suicide.

Las Vegas Mayor Carolyn Goodman described the shooter as a "crazed lunatic full of hate".

Who is Stephen Paddock?

The man who opened fire at concertgoers in Las Vegas last night was a local with no criminal convictions in the state of Nevada.

Stephen Paddock, 64, lived just 90 minutes outside Las Vegas in the city of Mesquite, where he bought a home in an upscale retirement community for just over $369,000 in 2015 according to public records.

He checked into the Mandalay last Thursday. He was reportedly armed with 18-20 weapons, including "AR-15-style and AK-47-style rifles" when he opened fire from a hotel room on the 32nd floor of the Mandalay Bay Resort, killing 59 and injuring at least 500.

He lived with his 62-year-old Australian partner Marilou Danley, whom police announced they wanted to question on Sunday night as they began their investigation into the horrific attack. She has since been found outside the country and is no longer considered a suspect.

A woman sits on a curb at the scene of a shooting outside of a music festival along the Las Vegas Strip. Photo / AP
A woman sits on a curb at the scene of a shooting outside of a music festival along the Las Vegas Strip. Photo / AP

Paddock had hunting and fishing licenses according to public records, as well as his pilot's license, but no criminal record in the state of Nevada.

Before he retired, he worked for as an internal auditor at Lockheed Martin for three years in the late 1980s, and later managed an apartment building in Mesquite, Texas.

Paddock was the son of Benjamin Hoskins Paddock, a serial bank robber who ended up on the FBI Most Wanted list in 1969 when he escaped from federal prison in Texas while serving a 20-year sentence.

The FBI kept him on the list for the next eight years, and eventually found him one year after he was removed from the list in 1978 outside an Oregon Bingo hall.

The agency said that the fugitive had been "diagnosed as psychopathic" and also had possible "suicidal tendencies".

Medics treat the wounded as Las Vegas police respond during an active shooter situation on the Las Vegas Strip in Las Vegas. Photo / AP
Medics treat the wounded as Las Vegas police respond during an active shooter situation on the Las Vegas Strip in Las Vegas. Photo / AP

Gunman a high stakes poker player

Before he opened fire on Monday at a country music festival on the Las Vegas Strip, Paddock was living out his retirement as a high-stakes gambler in a quiet town outside Las Vegas.

Paddock, 64, would disappear for days at a time, frequenting casinos with his longtime partner, neighbours said. Relatives also said Paddock had frequently visited Las Vegas to gamble and take in concerts.

Florida-based Eric Paddock said his brother often gambled in tens of thousands of dollars.

"My brother is not like you and me. He plays high-stakes video poker," he said. "He sends me a text that says he won $250,000 at the casino."

Eric Paddock said he showed the FBI three years of text messages from his brother and said he had no information whether Stephen Paddock had gambling debts or was financially troubled.

"I have absolutely no information he lost a bunch of money. The casino would know that," he said.

Eric Paddock said his brother previously worked as an accountant but also had real estate investments, including houses and apartments around Orlando. He said Stephen Paddock had no kids and plenty of money to play with.

Eric Paddock said he did not know of any mental illness, alcohol or drug problems in his brother's life.

'We are dumbfounded': Gunman's brother

Eric Paddock said his brother was a normal guy who must have "snapped" before carrying out the worst mass shooting in American history.

But he said there was "absolutely no indication he could do something like this" and said that Stephen had no political or religious affiliation.

He said: "He was just a guy. Something happened, he snapped or something."

"We know absolutely nothing, this is just... we are dumbfounded.

"We have absolutely no idea. Our condolences go to the victims and all their families."

Eric said that he and Stephen, 64, lived on different coasts and that they did not speak that often.

Isis has claimed responsibility for the shooting, but is yet to offer any proof.

Shooter had up to 20 weapons

The attack played out as Jason Aldean performed to close the third and final day of the Route 91 Harvest Music Festival, across the street from the resort.

More than 20,000 people were at the concert, and described the attack as "nonstop gunfire", which only stopped when the gunman reloaded his weapon.

Police said early Monday that they found more than 10 rifles in the room and that Paddock died of a self-inflicted gunshot wound.

However the Wall St Journal later reported the Vegas gunman had 18-20 weapons in the hotel room, including "AR-15-style and AK-47-style rifles".

He is believed to have acted alone, despite early reports that there may have been multiple shooters.

Images of the Mandalay Bay Resort after the attack show two large windows on the 32nd floor of the building completely blown out.

Paddock had been staying there since last Thursday, arriving on September 28.

Officials have searched his Mesquite home and closed off a large perimeter around the Nevada property to keep the public and media at bay.

Paddock used Danley's ID when he checked into the hotel, according to a source with knowledge of the investigation, despite the fact she was not with him during his stay.

Paddock and Danley lived in a upscale community that includes an 18-hole golf course, indoor and outdoor swimming pools and a recreation centre with gym.

Residents must be over the age of 55 and no children are allowed to live in the development of more than 1000 homes.

In addition to his pricey Nevada property, Paddock owned two planes and, according to FAA records, was certified as a private pilot back in 2003.

His address on that 2003 certification is listed as Mesquite, Texas, where he lived in a $200,000 home for 12 years from 1998 to 2010.

Records do not show him owning or living at any home between 2010 and 2012, when he moved to Reno after two decades in Texas.

Isis claims responsibility, police not convinced

Police have not said whether or not Paddock had ties to any domestic or foreign terror groups, but multiple sources - including his brother - have said he is not believed to have any connections.

Isis has claimed responsibility for the attack early Monday, saying the gunman was a recent convert to Islam but that claim was quickly discredited by multiple officials, who stated that there is no evidence to support that allegation.

In an interview on Monday morning, Eric Paddock spoke about how shocked he was to learn that his brother was the suspected gunman.

Eric said that his brother was "not an avid gunman" and "has no military background" while speaking with CBSN, adding that he had no idea how he might have been able to obtain automatic weapons.

"He had a couple of guns but they were all handgun, legal...he might have had one long gun, but he had them in a safe," explained Eric.

Eric stated later in that same interview: "His life is an open book. It's all in public record. Once again, there is nothing. He went to college. He had a job."

He also said that his brother had "no religious affiliation, no political affiliation," adding: "He just hung out."

Danley meanwhile was a nice woman who baked cookies for her mother-in-law said Eric, who conducted the interview outside his Florida home.

Chaotic scenes as gunfire stops a concert and people flee for their lives

Eric did admit that he and his brother do not speak often on account of the fact that they live on opposite coasts, but did share a recent text he received from his brother, asking how their 90-year-old mother was holding up in the wake of Hurricane Irma.

He closed out the interview by saying of his brother: "He's just a guy who lived in Mesquite who liked burritos."

During that interview Eric also made mention of the fact that his brother would often go to Las Vegas to gamble, and that Danley worked in one of the hotels as a hostess.

In an interview with Florida Today, two former neighbours of Paddock also spoke about his gambling, saying he would stay up all night with Danley placing bets.

"He seemed normal, other than that he lived by gambling. He was very open about that," revealed Sharon Judy.

"First time we ever met him, he handed us the key to the house and said, 'Hey, would keep an eye on the house, we're only going to be here every now and then'."

Judy lived next door to Paddock in Melbourne, Florida, where he and Danley had a home from 2013 through 2015, which they only visited a handful of times according to their neighbour.

That home was at Heritage Isle in Viera, another retirement community that only admitted residents over the age of 55.

Paddock bought his Mesquite, Nevada home at about the same time that he sold the Florida property.

Three years before, he filed a lawsuit against Cosmopolitan Hotels & Resorts following an incident that occurred at their Las Vegas casino.

Paddock spent two years in court fighting his case after submitting his initial complaint citing "Negligence - Premises Liability".

It was ultimately dismissed in late 2014 with prejudice, though exact details of the case were not available on the Clark County Courts website.